The present invention relates to an arrangement for treating substrates in a vacuum receptacle, such as, in particular, by means of physical or chemical coating processes or by means of an etching process, an apparatus for sputtering or vaporization, a cathode sputtering apparatus with a target operated as a magnetron, as well as a process for the uniform treatment of substrates.
When treating substrates, such as, in particular, when coating for example in a high vacuum, it can be of the greatest importance that the treatment or the coating takes place so as to be distributed uniformly or homogeneously over the entire surface. Especially in cases in which work takes place by means of working gases or reactive gases, it has been found that the gas inlet system represents a sensitive component with respect to the above described conditions.
In particular in etching and coating technology utilizing so-called plasmas, such as for example with cathode sputtering in a receptacle, in the presence of non-homogeneous partial pressures of the working or reactive gases, inhomogeneous surfaces or layer distributions result on a substrate to be coated, with respect to layer thickness, or layer properties, such as index of refraction, coefficient of extinction, layer tension, composition, etc.
Diverse attempts are known for solving this set of problems. It is, for one, suggested to compensate, by means of so-called getter surfaces and diaphragms, different partial pressures and, on the other hand, to avoid the so-called "poisoning" of the target through the gas required at the substrate for the reactive deposition.
For example, in EP-A-0 347 567, use of a diaphragm with interspace between target and substrate is suggested, with the gases being supplied into this interspace.
In S. Manly et al., J. Vac. Sci. Technol., 18(2), 195, 1981, it is suggested to dispose, between target and substrate, a shielding with a passage and to supply a reactive gas through a line system which encompasses this passage opening, with the outlet openings of this line system being directed toward the substrate.
In Schiller et al., Thin Solid Films, 64, 455, 1979, so-called getter surfaces are provided in the region of the target in order to prevent the "poisoning" of the target surface by the reactive gas which is introduced in the proximity of the substrate surface. These getter surfaces absorb the reactive gas, such as for example oxygen. In the proximity of the target surface, furthermore, an inert working gas is supplied in order to keep the reactive gas away from the target.
It is further suggested that a gas inlet arrangement comprise a buffer volume on which are provided several outlet openings, with the buffer volume being implemented so as to be significantly larger than the amplitudes of the conveying volume pulsations brought about by the gas inlet arrangement. As a rule, buffer volumes of this type are long buffer chambers with outlet openings disposed largely equidistantly in the longitudinal direction. The problem with buffer chambers of this type, also referred to as pipe gas showers, resides in that it is hardly possible to control the gas passage in all outlet openings since it is strongly dependent on the type of flow in the buffer chamber. It is indeed possible to dispose diaphragms or other flow impedances, in buffer chambers of this type, however, computations of such constructions is extremely complicated.
DE-OS-33 31 707 also described specific measures which are directed toward decoupling the effect of the reactive gas on the target or the substrate.
Lastly, in U.S. Pat. No. 4,931,158 a second discharge (auxiliary plasma) is even suggested in the proximity of the substrate. Again, a working gas is introduced near the target and a reactive gas is introduced near the substrate. The two plasmas are separated by means of a grid.
It is a disadvantage in all of these measures, that the coating rates are relatively low and, in addition, the danger of locally differing gas compositions or locally differing gas flows still exists and, consequently, the initially required homogeneity, for example of a coating, is still not ensured. Due to different gas compositions or different partial presses of the gas, moreover, small arc discharges can occur on the target.